These sections contain discussions of the pathogenic yeasts, the sporotricha, diphtheria, the bichemistry of antigens and antibodies, toxins and antitoxins, bacterial hemotoxins and antihemotoxins, the toxins and antitoxins of the vibrios, and the so-called bacterial aggressins. Several of the articles are entirely new and all of them have been brought down to date. Pick and Silberstein's treatment of the biochemistry of antigens is especially